P
Posting2002
- Jan 1, 1970
- 0
Hi, I have a design of a satellite antenna and a low noise amplifier, and
have a problem after connecting them together...right now, the connection is
like this:
1) Antenna -> LNB -> Spectrum analyzer
2) Antenna -> LNA -> LNB -> Spectrum analyzer
The Antenna is 25 dB of gain, LNA is 20 dB of gain. Input match of the
antenna (SMA connection) is better than 10 dB, LNA S11 and S22 are better
than 10 dB as well. Noise figure of LNA is 1 dB. LNB downconverts to IF
and has 20 dB of gain by itself.
The results of the spectrum analyzer show some kind of oscillatory behavior
in the system.
http://www.ece.uwaterloo.ca/~dbusuioc/comparison2.jpg
With connection (1) I get the blue graph, with connection (2) I get the
green and red graphs (tested 2 different LNAs).
I am thinking there is a mismatch problem in the antenna -> LNA or LNA ->
LNB. I've tested with a loss pad between LNA and LNB to see if the
oscillatory behavior is gone and it's only reduced in power but still
present.
Anybody have any suggestion or ideas?
Thanks,
/Dan
have a problem after connecting them together...right now, the connection is
like this:
1) Antenna -> LNB -> Spectrum analyzer
2) Antenna -> LNA -> LNB -> Spectrum analyzer
The Antenna is 25 dB of gain, LNA is 20 dB of gain. Input match of the
antenna (SMA connection) is better than 10 dB, LNA S11 and S22 are better
than 10 dB as well. Noise figure of LNA is 1 dB. LNB downconverts to IF
and has 20 dB of gain by itself.
The results of the spectrum analyzer show some kind of oscillatory behavior
in the system.
http://www.ece.uwaterloo.ca/~dbusuioc/comparison2.jpg
With connection (1) I get the blue graph, with connection (2) I get the
green and red graphs (tested 2 different LNAs).
I am thinking there is a mismatch problem in the antenna -> LNA or LNA ->
LNB. I've tested with a loss pad between LNA and LNB to see if the
oscillatory behavior is gone and it's only reduced in power but still
present.
Anybody have any suggestion or ideas?
Thanks,
/Dan